shims: TAILQ_FOREACH_SAFE is unavailable in glibc

TAILQ_FOREACH_SAFE is a BSD specific macro.  Provide a definition for it
in the Linux shims.  Modern glibc doesnt use the QUEUE_DEBUGGING macro,
remove it.

Author: compnerd

src/internal.h

@@ -356,14 +356,10 @@ DISPATCH_EXPORT DISPATCH_NOTHROW void dispatch_atfork_child(void);
 		do { (elm)->field.tqe_prev = NULL; } while (0)
 
 #if DISPATCH_DEBUG
-// sys/queue.h debugging
-#if defined(__linux__)
-#define QUEUE_MACRO_DEBUG 1
-#else
 #undef TRASHIT
 #define TRASHIT(x) do {(x) = (void *)-1;} while (0)
-#endif
 #endif // DISPATCH_DEBUG
+
 #define _TAILQ_TRASH_ENTRY(elm, field) do { \
 			TRASHIT((elm)->field.tqe_next); \
 			TRASHIT((elm)->field.tqe_prev); \

src/shims/linux_stubs.h

@@ -16,6 +16,16 @@
 #ifndef __DISPATCH__STUBS__INTERNAL
 #define __DISPATCH__STUBS__INTERNAL
 
+#if !defined(TAILQ_FOREACH_SAFE)
+#define TAILQ_FOREACH_SAFE(var, head, field, temp)                             \
+  for ((var) = TAILQ_FIRST((head));                                            \
+       (var) && ((temp) = TAILQ_NEXT((var), field), 1); (var) = (temp))
+#endif
+
+#if !defined(TRASHIT)
+#define TRASHIT(x) do { (x) = (void *)-1; } while (0)
+#endif
+
 /*
  * Stub out defines for some mach types and related macros
  */